Before we get to the myths, a quick word about me. The reason I’m called “The Rogue Nutritionist” is that I’m the one in the crowd pointing an unimpressed finger at boneheaded notions about nutrition, weight loss, diet and health. So as you might imagine, myth-busting is one of my favorite activities. In this column, I’ve chosen 10 of my favorite doozies. Some are new; some are old but still around despite being past their expiration dates; and some are enjoying an undeserved resurrection from the graveyard of bad ideas.

MYTH #1

As long as you eat healthy foods, you’ll lose weight.

I learned the hard way that this myth is just wishful thinking when I spent a week at a macrobiotic resort in Jamaica eating nothing but “healthy” food and wound up gaining almost six pounds! Sure, if you substitute broccoli and carrots for Death By Chocolate, you’ll lose weight, all other things being equal. But weight gain is caused by an array of factors including, but not limited to, calories and hormones. If you eat too much, even of nutritionist-approved foods like beans, fish, fruits and vegetables, you’ll eventually stimulate high levels of the fat-storing hormones and end up gaining weight. So before you scarf down an extra-large bag of veggie chips or raw almonds, keep in mind that healthy foods have calories, too.

MYTH #2:

Having a Body Mass Index (BMI) over 25 means you’re overweight and should drop a few pounds.

BMI—or as it’s sometimes called by health professionals, the “Baloney Mass Index”—is at best an imprecise mathematical estimate of obesity. It’s just as inaccurate a measure of health as the bathroom scale. What really matters in health is adiposity, or body fat, and the BMI does not take into account how much of your body weight is muscle and how much of it is fat. A football player with nine percent body fat and excellent aerobic fitness might tip the scales into BMI “obese” territory, just as a 5’5” non-exercising woman who weighs 125 pounds but has 35 percent body fat would rate as “healthy”. Don’t give the BMI more power than it deserves, which is no more and no less than the ordinary bathroom scale. This means if you’re muscular, don’t freak out if your BMI is high; and if you’re thin but inactive, don’t fool yourself into believing you’re healthy.

MYTH #3:

A vegetarian diet is always healthy.

When I was a trainer at Equinox gym back in the day, we had an expression: “Twinkie Vegetarians.” These were people who were adamant about “not eating anything with a face,” so they essentially lived on Cap’n Crunch and spaghetti—which yes, is technically a vegetarian diet, but probably the worst one in the world.

Vegetarian diets tend to be very high-carb diets, often including tons of starches and high-glycemic grains that can exacerbate problems related to insulin resistance, metabolic syndrome and diabetes. And even the best vegetarian diets can have significant nutritional deficits. For instance, there’s no vitamin B-12 in the plant kingdom (despite a huge amount of propaganda to the contrary). Vegetarian doesn’t automatically equal healthy, just as meat-eating doesn’t automatically equal unhealthy. As the saying goes, the devil is in the details.

What’s most important when it comes to nutrition are patterns of eating. Some healthy patterns can be primarily vegetarian, but others can be equally healthy and be Paleolithic (aka the Caveman Diet). Those patterns should almost definitely include a ton of vegetables, but healthy patterns can also include animal products such as grass-fed beef and wild salmon.

The point isn’t that vegetarian diets are bad, just that they’re not always good. Healthy patterns of eating come in all flavors.

MYTH #4:

People would be much healthier if they went gluten-free.

I’m no fan of gluten but it’s simply not true that gluten-free products are automatically better than ones containing gluten. Unfortunately, a lot of gluten-free products substitute equally unhealthy ingredients for gluten. As William Davis, MD, points out in his brilliant book, Wheat Belly: Lose the Wheat, Lose the Weight, and Find Your Path Back to Health (Rodale Books, 2011), modern-day dwarf wheat—which is what we’re all eating—contains all sorts of components in addition to gluten that can cause problems. For example, there’s amylopectin A, which triggers the formation of small, dense LDL-B particles that are a key culprit in heart disease. (LDL-B particles are the true bad cholesterol; the other type of LDL, LDL-A, is harmless.)

That said, I believe grains and gluten cause a lot more problems for a lot more people than we’ve previously believed. If you’re one of those folks—or suspect you might be—by all means go gluten-free or even grain-free; you may see some major improvements. If, however, you have no unexplained inability to lose weight, no brain fog, bloat or other reactions to grains (particularly wheat, barley, rice and oats), there’s no reason to assume that you’re going to reap great health benefits from going gluten-free. Gluten-free isn’t the whole picture and it’s not necessary for every single person.

MYTH #5:

Organic food is no healthier than non-organic food.

This myth was given a big boost by a recent study that compared the vitamin and mineral content of organic and non-organic foods and concluded that organic food didn’t have any more of these elements than non-organic food. That assertion totally obscures the real reason we eat organic food, namely because of what it doesn’t have: pesticides, chemicals, carcinogens, hormones, antibiotics, steroids and other garden-variety toxins.

In fact, the same study showed that only seven percent of the organic produce contained detectable residues of pesticides compared with 38 percent of conventional produce—something the media also conveniently neglected to mention. Also overlooked were the findings that organic produce contained more compounds known as phenols (which are believed to have cancer-fighting properties), that organic meat contained considerably lower levels of antibiotic-resistant bacteria, and that organic milk was higher in omega-3 fatty acids than conventional milk.

So even if it’s true that organic and non-organic produce have similar amounts of certain vitamins, that hardly makes them identical when it comes to many other nutritional issues.

MYTH #6:

The number of calories you eat is what determines weight loss.

This is another myth that has been perpetrated by the Diet Establishment for years, but that has recently been disproven. In a small study published in the JAMA: Journal of the American Medical Association, researchers compared three diets containing an equal number of calories—a low-fat diet, a low-carb diet and a low-glycemic diet—and then tracked how many calories people “burned up” on the three different regimes. The low-fat dieters burned the fewest calories and the low-carb dieters burned the most. This demonstrated that it’s not just the number of calories consumed that matters, it’s also where those calories come from. “The low-fat diet that has been the primary approach for more than a generation is actually the worst for most outcomes, with the worst effects on insulin resistance, triglycerides and HDL, or good cholesterol,” said David Ludwig, MD, PhD, one of the researchers involved in the study.

MYTH #7:

Having a glass or two of wine a day will help prevent cancer.

On the one hand, moderate consumption of alcohol has been shown to be associated with a reduction in cardiovascular risk. On the other, it raises the risk of breast cancer. (The latter finding was only true in women who were deficient in folic acid, however, so make sure you’ve got that covered—nearly all good multivitamins contain 400 to 800 mcg.) Keep in mind: “Moderate” consumption of alcohol means one to two drinks a day for men and one drink a day for women.

MYTH #8:

You should eat five to six small meals every two to three hours.

This myth came from the idea that eating “boosts” your metabolism. Unfortunately, that’s a misinterpretation of the facts. Yes, a few extra calories are burned by digesting food (called the Thermal Effect of Food, or TEF), but that accounts for only about 10 percent of calories consumed, and is not affected by how often you eat. Another theory behind this myth is that smaller, frequent meals prevent you from getting ravenously hungry, thereby reducing the risk that you’ll pig out at your next meal. But Americans have demonstrated time and again that they don’t know what small means when it comes to food. So you have people scarfing down 200- to 400-calorie “mini-meals” all day long in addition to their big breakfasts, giant lunches and oversized dinners and thus they wind up consuming many more calories at the end of the day.

Furthermore, mounting research is pointing to the fact that intermittent fasting—i.e., going without food for 12 hours or so at a time—has a lot of health benefits, including lowering the risks for cardiovascular disease and diabetes. Bottom line: Eat when you’re hungry and stop before you’re completely full.

MYTH #9:

When it comes to losing weight, exercise is more important than diet.

Actually, it’s exactly the opposite. The research on this is very clear, and also very disheartening for those of us who once believed this particular myth. Truth is, exercise is a terrible way to lose weight. (It is, however, absolutely necessary for keeping it off. And is good for a hundred other health reasons, but right now we’re talking about weight.) As fitness pros say, “You can’t out-train a bad diet.”

When it comes to weight loss, diet trumps exercise every time.

MYTH #10:

Taking raspberry ketones will speed weight loss.

Ever since raspberry ketones were featured on The Dr. Oz Show, you can’t walk into a GNC or Vitamin Shoppe without seeing signs, ads and big displays extolling their benefits as the latest and greatest miracle weight-loss supplement. But the only miraculous thing about raspberry ketones is their genius publicist. Because in truth, there have only been three small studies on raspberry ketones, all done on rodents and all done in Asia. One of the studies did show that the ketones—which are natural compounds found in raspberries that give the berries their pleasant smell—increased secretion of a hormone called adiponectin, which helps break down fat. The other studies showed that high amounts of ketones protected the rats from fat gain and increased fat burning slightly. Okay, maybe that’s promising enough to justify a decent human study, but it’s hardly enough to make raspberry ketones a super-miracle weight-loss pill. Ah, that it were. Alas, it’s not.

The bottom line about myths: The next time you hear about research claiming that a well-studied substance like omega-3s or vitamin D “doesn’t do anything,” raise an eyebrow over a skeptical eye. Remember, one study never proves anything. And the next time you hear about a study claiming that a substance delivers miraculous results, view it with the same skepticism. Remember: If it sounds too good to be true, it probably is.

Jonny Bowden, PhD, CNS, aka “The Rogue Nutritionist” (TM) is a nationally known expert on weight loss and the best-selling author of 14 books including “The 150 Healthiest Foods on Earth”, “Living Low Carb”, and the number one Amazon best seller, “The Great Cholesterol Myth”. Visit him at jonnybowden.com or follow him on twitter @jonnybowden.